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7 SERIES 700A11 INSTALLATION MANUAL
Operation Logic
Heating Mode
When the variable speed controls determine that heating
is needed in the space the blower will be turned on, the
compressor will be ramped to speed 6 and the loop pump
will be started. The compressor will continue to run at
speed 6 for 60 seconds for oil circulation. During the 60
second oil circulation the controls will calculate what speed
the compressor will need to operate at to maintain the set
point in the space. If the compressor is operating at speed
12 and the unit is unable to maintain set point the controls
will stage on the electric heat. Electric heat will not operate
unless the compressor is already running at speed 12. Every
30 minutes if the compressor has been operating lower
than speed 6, the controls will increase the compressor to
speed 6 for one minute for oil circulation.
Cooling Mode
When the variable speed controls determine that cooling
is needed in the space the blower will be turned on, the
reversing valve will be enabled, the compressor will be
ramped to speed 6, and the loop pump will be started. The
compressor will continue to run at speed 6 for 60 seconds
for oil circulation. During the 60 second oil circulation the
controls will calculate what speed the compressor will
need to operate at to maintain the set point in the space.
The compressor will be limited to a maximum of speed 9
for cooling. If additional capacity is needed SuperBoost
mode can be enabled from the thermostat allowing the
compressor to run at speeds higher than 9 for a period of
24 hours. Every 30 minutes if the compressor has been
operating lower than speed 6, the controls will increase the
compressor to speed 6 for one minute for oil circulation.
ECM Blower Motor
The variable speed controls will vary the ECM blower
output to maintain optimum air flow at each of the 12
compressor speeds. If dehumidification mode is selected
during the cooling operation the airflow will be varied to
allow for maximum moisture removal.
Variable Speed Loop Pump
The variable speed controls will operate the variable speed
loop pump similar to the way the ECM blower motor operates.
The speed of the pump will be increased as the compressor
speed is increased to maintain adequate water flow.
Safe Mode
The system has encountered an unsafe operating condition
that prevents automatic speed control, e.g. lost a sensor
signal. To avoid damage to the system, the drive is running
the compressor at a fixed speed of 2400 rpm awaiting the
problem to be solved and eventually returning to normal
operation. If the problem cannot be solved the drive stops
and issues an alarm. (See fault/alarm table.)
Derating
The VS compressor utilizes ‘envelope control’ to
maintain performance within operational limits and
improve reliability. To accomplish this, pressure sensors
for discharge and suction pressure as well as hot gas
temperature sensing are used to monitor the conditions
in which the compressor operates. The envelope does
vary based upon operating speed (rpm). When operating
out of these limits the control will attempt to improve the
situation by moderating the compressor speed for a larger
envelope. When this occurs it can be observed on the
Aurora control as an ‘E’ code. The control will automatically
try to resolve the situation. If the situation progresses, a
fault and lockout will be generated by the control.
